/*
** $Id: lstrlib.c,v 1.254.1.1 2017/04/19 17:29:57 roberto Exp $
** Standard library for string operations and pattern-matching
** See Copyright Notice in lua.h
*/

#define lstrlib_c
#define LUA_LIB

#include "lprefix.h"

#include <ctype.h>
#include <float.h>
#include <limits.h>
#include <locale.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "lua.h"

#include "lauxlib.h"
#include "lualib.h"

/*
** maximum number of captures that a pattern can do during
** pattern-matching. This limit is arbitrary, but must fit in
** an unsigned char.
*/
#if !defined(LUA_MAXCAPTURES)
#define LUA_MAXCAPTURES 32
#endif

/* macro to 'unsign' a character */
#define uchar(c) ((unsigned char)(c))

/*
** Some sizes are better limited to fit in 'int', but must also fit in
** 'size_t'. (We assume that 'lua_Integer' cannot be smaller than 'int'.)
*/
#define MAX_SIZET ((size_t)(~(size_t)0))

#define MAXSIZE \
  (sizeof(size_t) < sizeof(int) ? MAX_SIZET : (size_t)(INT_MAX))

static int str_len(lua_State *L)
{
  size_t l;
  luaL_checklstring(L, 1, &l);
  lua_pushinteger(L, (lua_Integer)l);
  return 1;
}

/* translate a relative string position: negative means back from end */
static lua_Integer posrelat(lua_Integer pos, size_t len)
{
  if (pos >= 0)
    return pos;
  else if (0u - (size_t)pos > len)
    return 0;
  else
    return (lua_Integer)len + pos + 1;
}

static int str_sub(lua_State *L)
{
  size_t l;
  const char *s = luaL_checklstring(L, 1, &l);
  lua_Integer start = posrelat(luaL_checkinteger(L, 2), l);
  lua_Integer end = posrelat(luaL_optinteger(L, 3, -1), l);
  if (start < 1)
    start = 1;
  if (end > (lua_Integer)l)
    end = l;
  if (start <= end)
    lua_pushlstring(L, s + start - 1, (size_t)(end - start) + 1);
  else
    lua_pushliteral(L, "");
  return 1;
}

static int str_reverse(lua_State *L)
{
  size_t l, i;
  luaL_Buffer b;
  const char *s = luaL_checklstring(L, 1, &l);
  char *p = luaL_buffinitsize(L, &b, l);
  for (i = 0; i < l; i++)
    p[i] = s[l - i - 1];
  luaL_pushresultsize(&b, l);
  return 1;
}

static int str_lower(lua_State *L)
{
  size_t l;
  size_t i;
  luaL_Buffer b;
  const char *s = luaL_checklstring(L, 1, &l);
  char *p = luaL_buffinitsize(L, &b, l);
  for (i = 0; i < l; i++)
    p[i] = tolower(uchar(s[i]));
  luaL_pushresultsize(&b, l);
  return 1;
}

static int str_upper(lua_State *L)
{
  size_t l;
  size_t i;
  luaL_Buffer b;
  const char *s = luaL_checklstring(L, 1, &l);
  char *p = luaL_buffinitsize(L, &b, l);
  for (i = 0; i < l; i++)
    p[i] = toupper(uchar(s[i]));
  luaL_pushresultsize(&b, l);
  return 1;
}

static int str_rep(lua_State *L)
{
  size_t l, lsep;
  const char *s = luaL_checklstring(L, 1, &l);
  lua_Integer n = luaL_checkinteger(L, 2);
  const char *sep = luaL_optlstring(L, 3, "", &lsep);
  if (n <= 0)
    lua_pushliteral(L, "");
  else if (l + lsep < l || l + lsep > MAXSIZE / n) /* may overflow? */
    return luaL_error(L, "resulting string too large");
  else
  {
    size_t totallen = (size_t)n * l + (size_t)(n - 1) * lsep;
    luaL_Buffer b;
    char *p = luaL_buffinitsize(L, &b, totallen);
    while (n-- > 1)
    { /* first n-1 copies (followed by separator) */
      memcpy(p, s, l * sizeof(char));
      p += l;
      if (lsep > 0)
      { /* empty 'memcpy' is not that cheap */
        memcpy(p, sep, lsep * sizeof(char));
        p += lsep;
      }
    }
    memcpy(p, s, l * sizeof(char)); /* last copy (not followed by separator) */
    luaL_pushresultsize(&b, totallen);
  }
  return 1;
}

static int str_byte(lua_State *L)
{
  size_t l;
  const char *s = luaL_checklstring(L, 1, &l);
  lua_Integer posi = posrelat(luaL_optinteger(L, 2, 1), l);
  lua_Integer pose = posrelat(luaL_optinteger(L, 3, posi), l);
  int n, i;
  if (posi < 1)
    posi = 1;
  if (pose > (lua_Integer)l)
    pose = l;
  if (posi > pose)
    return 0;                 /* empty interval; return no values */
  if (pose - posi >= INT_MAX) /* arithmetic overflow? */
    return luaL_error(L, "string slice too long");
  n = (int)(pose - posi) + 1;
  luaL_checkstack(L, n, "string slice too long");
  for (i = 0; i < n; i++)
    lua_pushinteger(L, uchar(s[posi + i - 1]));
  return n;
}

static int str_char(lua_State *L)
{
  int n = lua_gettop(L); /* number of arguments */
  int i;
  luaL_Buffer b;
  char *p = luaL_buffinitsize(L, &b, n);
  for (i = 1; i <= n; i++)
  {
    lua_Integer c = luaL_checkinteger(L, i);
    luaL_argcheck(L, uchar(c) == c, i, "value out of range");
    p[i - 1] = uchar(c);
  }
  luaL_pushresultsize(&b, n);
  return 1;
}

static int writer(lua_State *L, const void *b, size_t size, void *B)
{
  (void)L;
  luaL_addlstring((luaL_Buffer *)B, (const char *)b, size);
  return 0;
}

static int str_dump(lua_State *L)
{
  luaL_Buffer b;
  int strip = lua_toboolean(L, 2);
  luaL_checktype(L, 1, LUA_TFUNCTION);
  lua_settop(L, 1);
  luaL_buffinit(L, &b);
  if (lua_dump(L, writer, &b, strip) != 0)
    return luaL_error(L, "unable to dump given function");
  luaL_pushresult(&b);
  return 1;
}

/*
** {======================================================
** PATTERN MATCHING
** =======================================================
*/

#define CAP_UNFINISHED (-1)
#define CAP_POSITION (-2)

typedef struct MatchState
{
  const char *src_init; /* init of source string */
  const char *src_end;  /* end ('\0') of source string */
  const char *p_end;    /* end ('\0') of pattern */
  lua_State *L;
  int matchdepth;      /* control for recursive depth (to avoid C stack overflow) */
  unsigned char level; /* total number of captures (finished or unfinished) */
  struct
  {
    const char *init;
    ptrdiff_t len;
  } capture[LUA_MAXCAPTURES];
} MatchState;

/* recursive function */
static const char *match(MatchState *ms, const char *s, const char *p);

/* maximum recursion depth for 'match' */
#if !defined(MAXCCALLS)
#define MAXCCALLS 200
#endif

#define L_ESC '%'
#define SPECIALS "^$*+?.([%-"

static int check_capture(MatchState *ms, int l)
{
  l -= '1';
  if (l < 0 || l >= ms->level || ms->capture[l].len == CAP_UNFINISHED)
    return luaL_error(ms->L, "invalid capture index %%%d", l + 1);
  return l;
}

static int capture_to_close(MatchState *ms)
{
  int level = ms->level;
  for (level--; level >= 0; level--)
    if (ms->capture[level].len == CAP_UNFINISHED)
      return level;
  return luaL_error(ms->L, "invalid pattern capture");
}

static const char *classend(MatchState *ms, const char *p)
{
  switch (*p++)
  {
  case L_ESC:
  {
    if (p == ms->p_end)
      luaL_error(ms->L, "malformed pattern (ends with '%%')");
    return p + 1;
  }
  case '[':
  {
    if (*p == '^')
      p++;
    do
    { /* look for a ']' */
      if (p == ms->p_end)
        luaL_error(ms->L, "malformed pattern (missing ']')");
      if (*(p++) == L_ESC && p < ms->p_end)
        p++; /* skip escapes (e.g. '%]') */
    } while (*p != ']');
    return p + 1;
  }
  default:
  {
    return p;
  }
  }
}

static int match_class(int c, int cl)
{
  int res;
  switch (tolower(cl))
  {
  case 'a':
    res = isalpha(c);
    break;
  case 'c':
    res = iscntrl(c);
    break;
  case 'd':
    res = isdigit(c);
    break;
  case 'g':
    res = isgraph(c);
    break;
  case 'l':
    res = islower(c);
    break;
  case 'p':
    res = ispunct(c);
    break;
  case 's':
    res = isspace(c);
    break;
  case 'u':
    res = isupper(c);
    break;
  case 'w':
    res = isalnum(c);
    break;
  case 'x':
    res = isxdigit(c);
    break;
  case 'z':
    res = (c == 0);
    break; /* deprecated option */
  default:
    return (cl == c);
  }
  return (islower(cl) ? res : !res);
}

static int matchbracketclass(int c, const char *p, const char *ec)
{
  int sig = 1;
  if (*(p + 1) == '^')
  {
    sig = 0;
    p++; /* skip the '^' */
  }
  while (++p < ec)
  {
    if (*p == L_ESC)
    {
      p++;
      if (match_class(c, uchar(*p)))
        return sig;
    }
    else if ((*(p + 1) == '-') && (p + 2 < ec))
    {
      p += 2;
      if (uchar(*(p - 2)) <= c && c <= uchar(*p))
        return sig;
    }
    else if (uchar(*p) == c)
      return sig;
  }
  return !sig;
}

static int singlematch(MatchState *ms, const char *s, const char *p,
                       const char *ep)
{
  if (s >= ms->src_end)
    return 0;
  else
  {
    int c = uchar(*s);
    switch (*p)
    {
    case '.':
      return 1; /* matches any char */
    case L_ESC:
      return match_class(c, uchar(*(p + 1)));
    case '[':
      return matchbracketclass(c, p, ep - 1);
    default:
      return (uchar(*p) == c);
    }
  }
}

static const char *matchbalance(MatchState *ms, const char *s,
                                const char *p)
{
  if (p >= ms->p_end - 1)
    luaL_error(ms->L, "malformed pattern (missing arguments to '%%b')");
  if (*s != *p)
    return NULL;
  else
  {
    int b = *p;
    int e = *(p + 1);
    int cont = 1;
    while (++s < ms->src_end)
    {
      if (*s == e)
      {
        if (--cont == 0)
          return s + 1;
      }
      else if (*s == b)
        cont++;
    }
  }
  return NULL; /* string ends out of balance */
}

static const char *max_expand(MatchState *ms, const char *s,
                              const char *p, const char *ep)
{
  ptrdiff_t i = 0; /* counts maximum expand for item */
  while (singlematch(ms, s + i, p, ep))
    i++;
  /* keeps trying to match with the maximum repetitions */
  while (i >= 0)
  {
    const char *res = match(ms, (s + i), ep + 1);
    if (res)
      return res;
    i--; /* else didn't match; reduce 1 repetition to try again */
  }
  return NULL;
}

static const char *min_expand(MatchState *ms, const char *s,
                              const char *p, const char *ep)
{
  for (;;)
  {
    const char *res = match(ms, s, ep + 1);
    if (res != NULL)
      return res;
    else if (singlematch(ms, s, p, ep))
      s++; /* try with one more repetition */
    else
      return NULL;
  }
}

static const char *start_capture(MatchState *ms, const char *s,
                                 const char *p, int what)
{
  const char *res;
  int level = ms->level;
  if (level >= LUA_MAXCAPTURES)
    luaL_error(ms->L, "too many captures");
  ms->capture[level].init = s;
  ms->capture[level].len = what;
  ms->level = level + 1;
  if ((res = match(ms, s, p)) == NULL) /* match failed? */
    ms->level--;                       /* undo capture */
  return res;
}

static const char *end_capture(MatchState *ms, const char *s,
                               const char *p)
{
  int l = capture_to_close(ms);
  const char *res;
  ms->capture[l].len = s - ms->capture[l].init; /* close capture */
  if ((res = match(ms, s, p)) == NULL)          /* match failed? */
    ms->capture[l].len = CAP_UNFINISHED;        /* undo capture */
  return res;
}

static const char *match_capture(MatchState *ms, const char *s, int l)
{
  size_t len;
  l = check_capture(ms, l);
  len = ms->capture[l].len;
  if ((size_t)(ms->src_end - s) >= len &&
      memcmp(ms->capture[l].init, s, len) == 0)
    return s + len;
  else
    return NULL;
}

static const char *match(MatchState *ms, const char *s, const char *p)
{
  if (ms->matchdepth-- == 0)
    luaL_error(ms->L, "pattern too complex");
init: /* using goto's to optimize tail recursion */
  if (p != ms->p_end)
  { /* end of pattern? */
    switch (*p)
    {
    case '(':
    {                      /* start capture */
      if (*(p + 1) == ')') /* position capture? */
        s = start_capture(ms, s, p + 2, CAP_POSITION);
      else
        s = start_capture(ms, s, p + 1, CAP_UNFINISHED);
      break;
    }
    case ')':
    { /* end capture */
      s = end_capture(ms, s, p + 1);
      break;
    }
    case '$':
    {
      if ((p + 1) != ms->p_end)          /* is the '$' the last char in pattern? */
        goto dflt;                       /* no; go to default */
      s = (s == ms->src_end) ? s : NULL; /* check end of string */
      break;
    }
    case L_ESC:
    { /* escaped sequences not in the format class[*+?-]? */
      switch (*(p + 1))
      {
      case 'b':
      { /* balanced string? */
        s = matchbalance(ms, s, p + 2);
        if (s != NULL)
        {
          p += 4;
          goto init; /* return match(ms, s, p + 4); */
        }            /* else fail (s == NULL) */
        break;
      }
      case 'f':
      { /* frontier? */
        const char *ep;
        char previous;
        p += 2;
        if (*p != '[')
          luaL_error(ms->L, "missing '[' after '%%f' in pattern");
        ep = classend(ms, p); /* points to what is next */
        previous = (s == ms->src_init) ? '\0' : *(s - 1);
        if (!matchbracketclass(uchar(previous), p, ep - 1) &&
            matchbracketclass(uchar(*s), p, ep - 1))
        {
          p = ep;
          goto init; /* return match(ms, s, ep); */
        }
        s = NULL; /* match failed */
        break;
      }
      case '0':
      case '1':
      case '2':
      case '3':
      case '4':
      case '5':
      case '6':
      case '7':
      case '8':
      case '9':
      { /* capture results (%0-%9)? */
        s = match_capture(ms, s, uchar(*(p + 1)));
        if (s != NULL)
        {
          p += 2;
          goto init; /* return match(ms, s, p + 2) */
        }
        break;
      }
      default:
        goto dflt;
      }
      break;
    }
    default:
    dflt:
    {                                   /* pattern class plus optional suffix */
      const char *ep = classend(ms, p); /* points to optional suffix */
      /* does not match at least once? */
      if (!singlematch(ms, s, p, ep))
      {
        if (*ep == '*' || *ep == '?' || *ep == '-')
        { /* accept empty? */
          p = ep + 1;
          goto init; /* return match(ms, s, ep + 1); */
        }
        else        /* '+' or no suffix */
          s = NULL; /* fail */
      }
      else
      { /* matched once */
        switch (*ep)
        { /* handle optional suffix */
        case '?':
        { /* optional */
          const char *res;
          if ((res = match(ms, s + 1, ep + 1)) != NULL)
            s = res;
          else
          {
            p = ep + 1;
            goto init; /* else return match(ms, s, ep + 1); */
          }
          break;
        }
        case '+': /* 1 or more repetitions */
          s++;    /* 1 match already done */
          /* FALLTHROUGH */
        case '*': /* 0 or more repetitions */
          s = max_expand(ms, s, p, ep);
          break;
        case '-': /* 0 or more repetitions (minimum) */
          s = min_expand(ms, s, p, ep);
          break;
        default: /* no suffix */
          s++;
          p = ep;
          goto init; /* return match(ms, s + 1, ep); */
        }
      }
      break;
    }
    }
  }
  ms->matchdepth++;
  return s;
}

static const char *lmemfind(const char *s1, size_t l1,
                            const char *s2, size_t l2)
{
  if (l2 == 0)
    return s1; /* empty strings are everywhere */
  else if (l2 > l1)
    return NULL; /* avoids a negative 'l1' */
  else
  {
    const char *init; /* to search for a '*s2' inside 's1' */
    l2--;             /* 1st char will be checked by 'memchr' */
    l1 = l1 - l2;     /* 's2' cannot be found after that */
    while (l1 > 0 && (init = (const char *)memchr(s1, *s2, l1)) != NULL)
    {
      init++; /* 1st char is already checked */
      if (memcmp(init, s2 + 1, l2) == 0)
        return init - 1;
      else
      { /* correct 'l1' and 's1' to try again */
        l1 -= init - s1;
        s1 = init;
      }
    }
    return NULL; /* not found */
  }
}

static void push_onecapture(MatchState *ms, int i, const char *s,
                            const char *e)
{
  if (i >= ms->level)
  {
    if (i == 0)                         /* ms->level == 0, too */
      lua_pushlstring(ms->L, s, e - s); /* add whole match */
    else
      luaL_error(ms->L, "invalid capture index %%%d", i + 1);
  }
  else
  {
    ptrdiff_t l = ms->capture[i].len;
    if (l == CAP_UNFINISHED)
      luaL_error(ms->L, "unfinished capture");
    if (l == CAP_POSITION)
      lua_pushinteger(ms->L, (ms->capture[i].init - ms->src_init) + 1);
    else
      lua_pushlstring(ms->L, ms->capture[i].init, l);
  }
}

static int push_captures(MatchState *ms, const char *s, const char *e)
{
  int i;
  int nlevels = (ms->level == 0 && s) ? 1 : ms->level;
  luaL_checkstack(ms->L, nlevels, "too many captures");
  for (i = 0; i < nlevels; i++)
    push_onecapture(ms, i, s, e);
  return nlevels; /* number of strings pushed */
}

/* check whether pattern has no special characters */
static int nospecials(const char *p, size_t l)
{
  size_t upto = 0;
  do
  {
    if (strpbrk(p + upto, SPECIALS))
      return 0;                   /* pattern has a special character */
    upto += strlen(p + upto) + 1; /* may have more after \0 */
  } while (upto <= l);
  return 1; /* no special chars found */
}

static void prepstate(MatchState *ms, lua_State *L,
                      const char *s, size_t ls, const char *p, size_t lp)
{
  ms->L = L;
  ms->matchdepth = MAXCCALLS;
  ms->src_init = s;
  ms->src_end = s + ls;
  ms->p_end = p + lp;
}

static void reprepstate(MatchState *ms)
{
  ms->level = 0;
  lua_assert(ms->matchdepth == MAXCCALLS);
}

static int str_find_aux(lua_State *L, int find)
{
  size_t ls, lp;
  const char *s = luaL_checklstring(L, 1, &ls);
  const char *p = luaL_checklstring(L, 2, &lp);
  lua_Integer init = posrelat(luaL_optinteger(L, 3, 1), ls);
  if (init < 1)
    init = 1;
  else if (init > (lua_Integer)ls + 1)
  {                 /* start after string's end? */
    lua_pushnil(L); /* cannot find anything */
    return 1;
  }
  /* explicit request or no special characters? */
  if (find && (lua_toboolean(L, 4) || nospecials(p, lp)))
  {
    /* do a plain search */
    const char *s2 = lmemfind(s + init - 1, ls - (size_t)init + 1, p, lp);
    if (s2)
    {
      lua_pushinteger(L, (s2 - s) + 1);
      lua_pushinteger(L, (s2 - s) + lp);
      return 2;
    }
  }
  else
  {
    MatchState ms;
    const char *s1 = s + init - 1;
    int anchor = (*p == '^');
    if (anchor)
    {
      p++;
      lp--; /* skip anchor character */
    }
    prepstate(&ms, L, s, ls, p, lp);
    do
    {
      const char *res;
      reprepstate(&ms);
      if ((res = match(&ms, s1, p)) != NULL)
      {
        if (find)
        {
          lua_pushinteger(L, (s1 - s) + 1); /* start */
          lua_pushinteger(L, res - s);      /* end */
          return push_captures(&ms, NULL, 0) + 2;
        }
        else
          return push_captures(&ms, s1, res);
      }
    } while (s1++ < ms.src_end && !anchor);
  }
  lua_pushnil(L); /* not found */
  return 1;
}

static int str_find(lua_State *L)
{
  return str_find_aux(L, 1);
}

static int str_match(lua_State *L)
{
  return str_find_aux(L, 0);
}

/* state for 'gmatch' */
typedef struct GMatchState
{
  const char *src;       /* current position */
  const char *p;         /* pattern */
  const char *lastmatch; /* end of last match */
  MatchState ms;         /* match state */
} GMatchState;

static int gmatch_aux(lua_State *L)
{
  GMatchState *gm = (GMatchState *)lua_touserdata(L, lua_upvalueindex(3));
  const char *src;
  gm->ms.L = L;
  for (src = gm->src; src <= gm->ms.src_end; src++)
  {
    const char *e;
    reprepstate(&gm->ms);
    if ((e = match(&gm->ms, src, gm->p)) != NULL && e != gm->lastmatch)
    {
      gm->src = gm->lastmatch = e;
      return push_captures(&gm->ms, src, e);
    }
  }
  return 0; /* not found */
}

static int gmatch(lua_State *L)
{
  size_t ls, lp;
  const char *s = luaL_checklstring(L, 1, &ls);
  const char *p = luaL_checklstring(L, 2, &lp);
  GMatchState *gm;
  lua_settop(L, 2); /* keep them on closure to avoid being collected */
  gm = (GMatchState *)lua_newuserdata(L, sizeof(GMatchState));
  prepstate(&gm->ms, L, s, ls, p, lp);
  gm->src = s;
  gm->p = p;
  gm->lastmatch = NULL;
  lua_pushcclosure(L, gmatch_aux, 3);
  return 1;
}

static void add_s(MatchState *ms, luaL_Buffer *b, const char *s,
                  const char *e)
{
  size_t l, i;
  lua_State *L = ms->L;
  const char *news = lua_tolstring(L, 3, &l);
  for (i = 0; i < l; i++)
  {
    if (news[i] != L_ESC)
      luaL_addchar(b, news[i]);
    else
    {
      i++; /* skip ESC */
      if (!isdigit(uchar(news[i])))
      {
        if (news[i] != L_ESC)
          luaL_error(L, "invalid use of '%c' in replacement string", L_ESC);
        luaL_addchar(b, news[i]);
      }
      else if (news[i] == '0')
        luaL_addlstring(b, s, e - s);
      else
      {
        push_onecapture(ms, news[i] - '1', s, e);
        luaL_tolstring(L, -1, NULL); /* if number, convert it to string */
        lua_remove(L, -2);           /* remove original value */
        luaL_addvalue(b);            /* add capture to accumulated result */
      }
    }
  }
}

static void add_value(MatchState *ms, luaL_Buffer *b, const char *s,
                      const char *e, int tr)
{
  lua_State *L = ms->L;
  switch (tr)
  {
  case LUA_TFUNCTION:
  {
    int n;
    lua_pushvalue(L, 3);
    n = push_captures(ms, s, e);
    lua_call(L, n, 1);
    break;
  }
  case LUA_TTABLE:
  {
    push_onecapture(ms, 0, s, e);
    lua_gettable(L, 3);
    break;
  }
  default:
  { /* LUA_TNUMBER or LUA_TSTRING */
    add_s(ms, b, s, e);
    return;
  }
  }
  if (!lua_toboolean(L, -1))
  { /* nil or false? */
    lua_pop(L, 1);
    lua_pushlstring(L, s, e - s); /* keep original text */
  }
  else if (!lua_isstring(L, -1))
    luaL_error(L, "invalid replacement value (a %s)", luaL_typename(L, -1));
  luaL_addvalue(b); /* add result to accumulator */
}

static int str_gsub(lua_State *L)
{
  size_t srcl, lp;
  const char *src = luaL_checklstring(L, 1, &srcl);    /* subject */
  const char *p = luaL_checklstring(L, 2, &lp);        /* pattern */
  const char *lastmatch = NULL;                        /* end of last match */
  int tr = lua_type(L, 3);                             /* replacement type */
  lua_Integer max_s = luaL_optinteger(L, 4, srcl + 1); /* max replacements */
  int anchor = (*p == '^');
  lua_Integer n = 0; /* replacement count */
  MatchState ms;
  luaL_Buffer b;
  luaL_argcheck(L, tr == LUA_TNUMBER || tr == LUA_TSTRING || tr == LUA_TFUNCTION || tr == LUA_TTABLE, 3,
                "string/function/table expected");
  luaL_buffinit(L, &b);
  if (anchor)
  {
    p++;
    lp--; /* skip anchor character */
  }
  prepstate(&ms, L, src, srcl, p, lp);
  while (n < max_s)
  {
    const char *e;
    reprepstate(&ms); /* (re)prepare state for new match */
    if ((e = match(&ms, src, p)) != NULL && e != lastmatch)
    { /* match? */
      n++;
      add_value(&ms, &b, src, e, tr); /* add replacement to buffer */
      src = lastmatch = e;
    }
    else if (src < ms.src_end) /* otherwise, skip one character */
      luaL_addchar(&b, *src++);
    else
      break; /* end of subject */
    if (anchor)
      break;
  }
  luaL_addlstring(&b, src, ms.src_end - src);
  luaL_pushresult(&b);
  lua_pushinteger(L, n); /* number of substitutions */
  return 2;
}

/* }====================================================== */

/*
** {======================================================
** STRING FORMAT
** =======================================================
*/

#if !defined(lua_number2strx) /* { */

/*
** Hexadecimal floating-point formatter
*/

#include <math.h>

#define SIZELENMOD (sizeof(LUA_NUMBER_FRMLEN) / sizeof(char))

/*
** Number of bits that goes into the first digit. It can be any value
** between 1 and 4; the following definition tries to align the number
** to nibble boundaries by making what is left after that first digit a
** multiple of 4.
*/
#define L_NBFD ((l_mathlim(MANT_DIG) - 1) % 4 + 1)

/*
** Add integer part of 'x' to buffer and return new 'x'
*/
static lua_Number adddigit(char *buff, int n, lua_Number x)
{
  lua_Number dd = l_mathop(floor)(x); /* get integer part from 'x' */
  int d = (int)dd;
  buff[n] = (d < 10 ? d + '0' : d - 10 + 'a'); /* add to buffer */
  return x - dd;                               /* return what is left */
}

static int num2straux(char *buff, int sz, lua_Number x)
{
  /* if 'inf' or 'NaN', format it like '%g' */
  if (x != x || x == (lua_Number)HUGE_VAL || x == -(lua_Number)HUGE_VAL)
    return l_sprintf(buff, sz, LUA_NUMBER_FMT, (LUAI_UACNUMBER)x);
  else if (x == 0)
  { /* can be -0... */
    /* create "0" or "-0" followed by exponent */
    return l_sprintf(buff, sz, LUA_NUMBER_FMT "x0p+0", (LUAI_UACNUMBER)x);
  }
  else
  {
    int e;
    lua_Number m = l_mathop(frexp)(x, &e); /* 'x' fraction and exponent */
    int n = 0;                             /* character count */
    if (m < 0)
    {                  /* is number negative? */
      buff[n++] = '-'; /* add signal */
      m = -m;          /* make it positive */
    }
    buff[n++] = '0';
    buff[n++] = 'x';                            /* add "0x" */
    m = adddigit(buff, n++, m * (1 << L_NBFD)); /* add first digit */
    e -= L_NBFD;                                /* this digit goes before the radix point */
    if (m > 0)
    {                                      /* more digits? */
      buff[n++] = lua_getlocaledecpoint(); /* add radix point */
      do
      { /* add as many digits as needed */
        m = adddigit(buff, n++, m * 16);
      } while (m > 0);
    }
    n += l_sprintf(buff + n, sz - n, "p%+d", e); /* add exponent */
    lua_assert(n < sz);
    return n;
  }
}

static int lua_number2strx(lua_State *L, char *buff, int sz,
                           const char *fmt, lua_Number x)
{
  int n = num2straux(buff, sz, x);
  if (fmt[SIZELENMOD] == 'A')
  {
    int i;
    for (i = 0; i < n; i++)
      buff[i] = toupper(uchar(buff[i]));
  }
  else if (fmt[SIZELENMOD] != 'a')
    return luaL_error(L, "modifiers for format '%%a'/'%%A' not implemented");
  return n;
}

#endif /* } */

/*
** Maximum size of each formatted item. This maximum size is produced
** by format('%.99f', -maxfloat), and is equal to 99 + 3 ('-', '.',
** and '\0') + number of decimal digits to represent maxfloat (which
** is maximum exponent + 1). (99+3+1 then rounded to 120 for "extra
** expenses", such as locale-dependent stuff)
*/
#define MAX_ITEM (120 + l_mathlim(MAX_10_EXP))

/* valid flags in a format specification */
#define FLAGS "-+ #0"

/*
** maximum size of each format specification (such as "%-099.99d")
*/
#define MAX_FORMAT 32

static void addquoted(luaL_Buffer *b, const char *s, size_t len)
{
  luaL_addchar(b, '"');
  while (len--)
  {
    if (*s == '"' || *s == '\\' || *s == '\n')
    {
      luaL_addchar(b, '\\');
      luaL_addchar(b, *s);
    }
    else if (iscntrl(uchar(*s)))
    {
      char buff[10];
      if (!isdigit(uchar(*(s + 1))))
        l_sprintf(buff, sizeof(buff), "\\%d", (int)uchar(*s));
      else
        l_sprintf(buff, sizeof(buff), "\\%03d", (int)uchar(*s));
      luaL_addstring(b, buff);
    }
    else
      luaL_addchar(b, *s);
    s++;
  }
  luaL_addchar(b, '"');
}

/*
** Ensures the 'buff' string uses a dot as the radix character.
*/
static void checkdp(char *buff, int nb)
{
  if (memchr(buff, '.', nb) == NULL)
  {                                       /* no dot? */
    char point = lua_getlocaledecpoint(); /* try locale point */
    char *ppoint = (char *)memchr(buff, point, nb);
    if (ppoint)
      *ppoint = '.'; /* change it to a dot */
  }
}

static void addliteral(lua_State *L, luaL_Buffer *b, int arg)
{
  switch (lua_type(L, arg))
  {
  case LUA_TSTRING:
  {
    size_t len;
    const char *s = lua_tolstring(L, arg, &len);
    addquoted(b, s, len);
    break;
  }
  case LUA_TNUMBER:
  {
    char *buff = luaL_prepbuffsize(b, MAX_ITEM);
    int nb;
    if (!lua_isinteger(L, arg))
    {                                      /* float? */
      lua_Number n = lua_tonumber(L, arg); /* write as hexa ('%a') */
      nb = lua_number2strx(L, buff, MAX_ITEM, "%" LUA_NUMBER_FRMLEN "a", n);
      checkdp(buff, nb); /* ensure it uses a dot */
    }
    else
    { /* integers */
      lua_Integer n = lua_tointeger(L, arg);
      const char *format = (n == LUA_MININTEGER)              /* corner case? */
                               ? "0x%" LUA_INTEGER_FRMLEN "x" /* use hexa */
                               : LUA_INTEGER_FMT;             /* else use default format */
      nb = l_sprintf(buff, MAX_ITEM, format, (LUAI_UACINT)n);
    }
    luaL_addsize(b, nb);
    break;
  }
  case LUA_TNIL:
  case LUA_TBOOLEAN:
  {
    luaL_tolstring(L, arg, NULL);
    luaL_addvalue(b);
    break;
  }
  default:
  {
    luaL_argerror(L, arg, "value has no literal form");
  }
  }
}

static const char *scanformat(lua_State *L, const char *strfrmt, char *form)
{
  const char *p = strfrmt;
  while (*p != '\0' && strchr(FLAGS, *p) != NULL)
    p++; /* skip flags */
  if ((size_t)(p - strfrmt) >= sizeof(FLAGS) / sizeof(char))
    luaL_error(L, "invalid format (repeated flags)");
  if (isdigit(uchar(*p)))
    p++; /* skip width */
  if (isdigit(uchar(*p)))
    p++; /* (2 digits at most) */
  if (*p == '.')
  {
    p++;
    if (isdigit(uchar(*p)))
      p++; /* skip precision */
    if (isdigit(uchar(*p)))
      p++; /* (2 digits at most) */
  }
  if (isdigit(uchar(*p)))
    luaL_error(L, "invalid format (width or precision too long)");
  *(form++) = '%';
  memcpy(form, strfrmt, ((p - strfrmt) + 1) * sizeof(char));
  form += (p - strfrmt) + 1;
  *form = '\0';
  return p;
}

/*
** add length modifier into formats
*/
static void addlenmod(char *form, const char *lenmod)
{
  size_t l = strlen(form);
  size_t lm = strlen(lenmod);
  char spec = form[l - 1];
  strcpy(form + l - 1, lenmod);
  form[l + lm - 1] = spec;
  form[l + lm] = '\0';
}

static int str_format(lua_State *L)
{
  int top = lua_gettop(L);
  int arg = 1;
  size_t sfl;
  const char *strfrmt = luaL_checklstring(L, arg, &sfl);
  const char *strfrmt_end = strfrmt + sfl;
  luaL_Buffer b;
  luaL_buffinit(L, &b);
  while (strfrmt < strfrmt_end)
  {
    if (*strfrmt != L_ESC)
      luaL_addchar(&b, *strfrmt++);
    else if (*++strfrmt == L_ESC)
      luaL_addchar(&b, *strfrmt++); /* %% */
    else
    {                                               /* format item */
      char form[MAX_FORMAT];                        /* to store the format ('%...') */
      char *buff = luaL_prepbuffsize(&b, MAX_ITEM); /* to put formatted item */
      int nb = 0;                                   /* number of bytes in added item */
      if (++arg > top)
        luaL_argerror(L, arg, "no value");
      strfrmt = scanformat(L, strfrmt, form);
      switch (*strfrmt++)
      {
      case 'c':
      {
        nb = l_sprintf(buff, MAX_ITEM, form, (int)luaL_checkinteger(L, arg));
        break;
      }
      case 'd':
      case 'i':
      case 'o':
      case 'u':
      case 'x':
      case 'X':
      {
        lua_Integer n = luaL_checkinteger(L, arg);
        addlenmod(form, LUA_INTEGER_FRMLEN);
        nb = l_sprintf(buff, MAX_ITEM, form, (LUAI_UACINT)n);
        break;
      }
      case 'a':
      case 'A':
        addlenmod(form, LUA_NUMBER_FRMLEN);
        nb = lua_number2strx(L, buff, MAX_ITEM, form,
                             luaL_checknumber(L, arg));
        break;
      case 'e':
      case 'E':
      case 'f':
      case 'g':
      case 'G':
      {
        lua_Number n = luaL_checknumber(L, arg);
        addlenmod(form, LUA_NUMBER_FRMLEN);
        nb = l_sprintf(buff, MAX_ITEM, form, (LUAI_UACNUMBER)n);
        break;
      }
      case 'q':
      {
        addliteral(L, &b, arg);
        break;
      }
      case 's':
      {
        size_t l;
        const char *s = luaL_tolstring(L, arg, &l);
        if (form[2] == '\0') /* no modifiers? */
          luaL_addvalue(&b); /* keep entire string */
        else
        {
          luaL_argcheck(L, l == strlen(s), arg, "string contains zeros");
          if (!strchr(form, '.') && l >= 100)
          {
            /* no precision and string is too long to be formatted */
            luaL_addvalue(&b); /* keep entire string */
          }
          else
          { /* format the string into 'buff' */
            nb = l_sprintf(buff, MAX_ITEM, form, s);
            lua_pop(L, 1); /* remove result from 'luaL_tolstring' */
          }
        }
        break;
      }
      default:
      { /* also treat cases 'pnLlh' */
        return luaL_error(L, "invalid option '%%%c' to 'format'",
                          *(strfrmt - 1));
      }
      }
      lua_assert(nb < MAX_ITEM);
      luaL_addsize(&b, nb);
    }
  }
  luaL_pushresult(&b);
  return 1;
}

/* }====================================================== */

/*
** {======================================================
** PACK/UNPACK
** =======================================================
*/

/* value used for padding */
#if !defined(LUAL_PACKPADBYTE)
#define LUAL_PACKPADBYTE 0x00
#endif

/* maximum size for the binary representation of an integer */
#define MAXINTSIZE 16

/* number of bits in a character */
#define NB CHAR_BIT

/* mask for one character (NB 1's) */
#define MC ((1 << NB) - 1)

/* size of a lua_Integer */
#define SZINT ((int)sizeof(lua_Integer))

/* dummy union to get native endianness */
static const union {
  int dummy;
  char little; /* true iff machine is little endian */
} nativeendian = {1};

/* dummy structure to get native alignment requirements */
struct cD
{
  char c;
  union {
    double d;
    void *p;
    lua_Integer i;
    lua_Number n;
  } u;
};

#define MAXALIGN (offsetof(struct cD, u))

/*
** Union for serializing floats
*/
typedef union Ftypes {
  float f;
  double d;
  lua_Number n;
  char buff[5 * sizeof(lua_Number)]; /* enough for any float type */
} Ftypes;

/*
** information to pack/unpack stuff
*/
typedef struct Header
{
  lua_State *L;
  int islittle;
  int maxalign;
} Header;

/*
** options for pack/unpack
*/
typedef enum KOption
{
  Kint,       /* signed integers */
  Kuint,      /* unsigned integers */
  Kfloat,     /* floating-point numbers */
  Kchar,      /* fixed-length strings */
  Kstring,    /* strings with prefixed length */
  Kzstr,      /* zero-terminated strings */
  Kpadding,   /* padding */
  Kpaddalign, /* padding for alignment */
  Knop        /* no-op (configuration or spaces) */
} KOption;

/*
** Read an integer numeral from string 'fmt' or return 'df' if
** there is no numeral
*/
static int digit(int c) { return '0' <= c && c <= '9'; }

static int getnum(const char **fmt, int df)
{
  if (!digit(**fmt)) /* no number? */
    return df;       /* return default value */
  else
  {
    int a = 0;
    do
    {
      a = a * 10 + (*((*fmt)++) - '0');
    } while (digit(**fmt) && a <= ((int)MAXSIZE - 9) / 10);
    return a;
  }
}

/*
** Read an integer numeral and raises an error if it is larger
** than the maximum size for integers.
*/
static int getnumlimit(Header *h, const char **fmt, int df)
{
  int sz = getnum(fmt, df);
  if (sz > MAXINTSIZE || sz <= 0)
    return luaL_error(h->L, "integral size (%d) out of limits [1,%d]",
                      sz, MAXINTSIZE);
  return sz;
}

/*
** Initialize Header
*/
static void initheader(lua_State *L, Header *h)
{
  h->L = L;
  h->islittle = nativeendian.little;
  h->maxalign = 1;
}

/*
** Read and classify next option. 'size' is filled with option's size.
*/
static KOption getoption(Header *h, const char **fmt, int *size)
{
  int opt = *((*fmt)++);
  *size = 0; /* default */
  switch (opt)
  {
  case 'b':
    *size = sizeof(char);
    return Kint;
  case 'B':
    *size = sizeof(char);
    return Kuint;
  case 'h':
    *size = sizeof(short);
    return Kint;
  case 'H':
    *size = sizeof(short);
    return Kuint;
  case 'l':
    *size = sizeof(long);
    return Kint;
  case 'L':
    *size = sizeof(long);
    return Kuint;
  case 'j':
    *size = sizeof(lua_Integer);
    return Kint;
  case 'J':
    *size = sizeof(lua_Integer);
    return Kuint;
  case 'T':
    *size = sizeof(size_t);
    return Kuint;
  case 'f':
    *size = sizeof(float);
    return Kfloat;
  case 'd':
    *size = sizeof(double);
    return Kfloat;
  case 'n':
    *size = sizeof(lua_Number);
    return Kfloat;
  case 'i':
    *size = getnumlimit(h, fmt, sizeof(int));
    return Kint;
  case 'I':
    *size = getnumlimit(h, fmt, sizeof(int));
    return Kuint;
  case 's':
    *size = getnumlimit(h, fmt, sizeof(size_t));
    return Kstring;
  case 'c':
    *size = getnum(fmt, -1);
    if (*size == -1)
      luaL_error(h->L, "missing size for format option 'c'");
    return Kchar;
  case 'z':
    return Kzstr;
  case 'x':
    *size = 1;
    return Kpadding;
  case 'X':
    return Kpaddalign;
  case ' ':
    break;
  case '<':
    h->islittle = 1;
    break;
  case '>':
    h->islittle = 0;
    break;
  case '=':
    h->islittle = nativeendian.little;
    break;
  case '!':
    h->maxalign = getnumlimit(h, fmt, MAXALIGN);
    break;
  default:
    luaL_error(h->L, "invalid format option '%c'", opt);
  }
  return Knop;
}

/*
** Read, classify, and fill other details about the next option.
** 'psize' is filled with option's size, 'notoalign' with its
** alignment requirements.
** Local variable 'size' gets the size to be aligned. (Kpadal option
** always gets its full alignment, other options are limited by
** the maximum alignment ('maxalign'). Kchar option needs no alignment
** despite its size.
*/
static KOption getdetails(Header *h, size_t totalsize,
                          const char **fmt, int *psize, int *ntoalign)
{
  KOption opt = getoption(h, fmt, psize);
  int align = *psize; /* usually, alignment follows size */
  if (opt == Kpaddalign)
  { /* 'X' gets alignment from following option */
    if (**fmt == '\0' || getoption(h, fmt, &align) == Kchar || align == 0)
      luaL_argerror(h->L, 1, "invalid next option for option 'X'");
  }
  if (align <= 1 || opt == Kchar) /* need no alignment? */
    *ntoalign = 0;
  else
  {
    if (align > h->maxalign) /* enforce maximum alignment */
      align = h->maxalign;
    if ((align & (align - 1)) != 0) /* is 'align' not a power of 2? */
      luaL_argerror(h->L, 1, "format asks for alignment not power of 2");
    *ntoalign = (align - (int)(totalsize & (align - 1))) & (align - 1);
  }
  return opt;
}

/*
** Pack integer 'n' with 'size' bytes and 'islittle' endianness.
** The final 'if' handles the case when 'size' is larger than
** the size of a Lua integer, correcting the extra sign-extension
** bytes if necessary (by default they would be zeros).
*/
static void packint(luaL_Buffer *b, lua_Unsigned n,
                    int islittle, int size, int neg)
{
  char *buff = luaL_prepbuffsize(b, size);
  int i;
  buff[islittle ? 0 : size - 1] = (char)(n & MC); /* first byte */
  for (i = 1; i < size; i++)
  {
    n >>= NB;
    buff[islittle ? i : size - 1 - i] = (char)(n & MC);
  }
  if (neg && size > SZINT)
  {                                /* negative number need sign extension? */
    for (i = SZINT; i < size; i++) /* correct extra bytes */
      buff[islittle ? i : size - 1 - i] = (char)MC;
  }
  luaL_addsize(b, size); /* add result to buffer */
}

/*
** Copy 'size' bytes from 'src' to 'dest', correcting endianness if
** given 'islittle' is different from native endianness.
*/
static void copywithendian(volatile char *dest, volatile const char *src,
                           int size, int islittle)
{
  if (islittle == nativeendian.little)
  {
    while (size-- != 0)
      *(dest++) = *(src++);
  }
  else
  {
    dest += size - 1;
    while (size-- != 0)
      *(dest--) = *(src++);
  }
}

static int str_pack(lua_State *L)
{
  luaL_Buffer b;
  Header h;
  const char *fmt = luaL_checkstring(L, 1); /* format string */
  int arg = 1;                              /* current argument to pack */
  size_t totalsize = 0;                     /* accumulate total size of result */
  initheader(L, &h);
  lua_pushnil(L); /* mark to separate arguments from string buffer */
  luaL_buffinit(L, &b);
  while (*fmt != '\0')
  {
    int size, ntoalign;
    KOption opt = getdetails(&h, totalsize, &fmt, &size, &ntoalign);
    totalsize += ntoalign + size;
    while (ntoalign-- > 0)
      luaL_addchar(&b, LUAL_PACKPADBYTE); /* fill alignment */
    arg++;
    switch (opt)
    {
    case Kint:
    { /* signed integers */
      lua_Integer n = luaL_checkinteger(L, arg);
      if (size < SZINT)
      { /* need overflow check? */
        lua_Integer lim = (lua_Integer)1 << ((size * NB) - 1);
        luaL_argcheck(L, -lim <= n && n < lim, arg, "integer overflow");
      }
      packint(&b, (lua_Unsigned)n, h.islittle, size, (n < 0));
      break;
    }
    case Kuint:
    { /* unsigned integers */
      lua_Integer n = luaL_checkinteger(L, arg);
      if (size < SZINT) /* need overflow check? */
        luaL_argcheck(L, (lua_Unsigned)n < ((lua_Unsigned)1 << (size * NB)),
                      arg, "unsigned overflow");
      packint(&b, (lua_Unsigned)n, h.islittle, size, 0);
      break;
    }
    case Kfloat:
    { /* floating-point options */
      volatile Ftypes u;
      char *buff = luaL_prepbuffsize(&b, size);
      lua_Number n = luaL_checknumber(L, arg); /* get argument */
      if (size == sizeof(u.f))
        u.f = (float)n; /* copy it into 'u' */
      else if (size == sizeof(u.d))
        u.d = (double)n;
      else
        u.n = n;
      /* move 'u' to final result, correcting endianness if needed */
      copywithendian(buff, u.buff, size, h.islittle);
      luaL_addsize(&b, size);
      break;
    }
    case Kchar:
    { /* fixed-size string */
      size_t len;
      const char *s = luaL_checklstring(L, arg, &len);
      luaL_argcheck(L, len <= (size_t)size, arg,
                    "string longer than given size");
      luaL_addlstring(&b, s, len); /* add string */
      while (len++ < (size_t)size) /* pad extra space */
        luaL_addchar(&b, LUAL_PACKPADBYTE);
      break;
    }
    case Kstring:
    { /* strings with length count */
      size_t len;
      const char *s = luaL_checklstring(L, arg, &len);
      luaL_argcheck(L, size >= (int)sizeof(size_t) || len < ((size_t)1 << (size * NB)),
                    arg, "string length does not fit in given size");
      packint(&b, (lua_Unsigned)len, h.islittle, size, 0); /* pack length */
      luaL_addlstring(&b, s, len);
      totalsize += len;
      break;
    }
    case Kzstr:
    { /* zero-terminated string */
      size_t len;
      const char *s = luaL_checklstring(L, arg, &len);
      luaL_argcheck(L, strlen(s) == len, arg, "string contains zeros");
      luaL_addlstring(&b, s, len);
      luaL_addchar(&b, '\0'); /* add zero at the end */
      totalsize += len + 1;
      break;
    }
    case Kpadding:
      luaL_addchar(&b, LUAL_PACKPADBYTE); /* FALLTHROUGH */
    case Kpaddalign:
    case Knop:
      arg--; /* undo increment */
      break;
    }
  }
  luaL_pushresult(&b);
  return 1;
}

static int str_packsize(lua_State *L)
{
  Header h;
  const char *fmt = luaL_checkstring(L, 1); /* format string */
  size_t totalsize = 0;                     /* accumulate total size of result */
  initheader(L, &h);
  while (*fmt != '\0')
  {
    int size, ntoalign;
    KOption opt = getdetails(&h, totalsize, &fmt, &size, &ntoalign);
    size += ntoalign; /* total space used by option */
    luaL_argcheck(L, totalsize <= MAXSIZE - size, 1,
                  "format result too large");
    totalsize += size;
    switch (opt)
    {
    case Kstring: /* strings with length count */
    case Kzstr:   /* zero-terminated string */
      luaL_argerror(L, 1, "variable-length format");
      /* call never return, but to avoid warnings: */ /* FALLTHROUGH */
    default:
      break;
    }
  }
  lua_pushinteger(L, (lua_Integer)totalsize);
  return 1;
}

/*
** Unpack an integer with 'size' bytes and 'islittle' endianness.
** If size is smaller than the size of a Lua integer and integer
** is signed, must do sign extension (propagating the sign to the
** higher bits); if size is larger than the size of a Lua integer,
** it must check the unread bytes to see whether they do not cause an
** overflow.
*/
static lua_Integer unpackint(lua_State *L, const char *str,
                             int islittle, int size, int issigned)
{
  lua_Unsigned res = 0;
  int i;
  int limit = (size <= SZINT) ? size : SZINT;
  for (i = limit - 1; i >= 0; i--)
  {
    res <<= NB;
    res |= (lua_Unsigned)(unsigned char)str[islittle ? i : size - 1 - i];
  }
  if (size < SZINT)
  { /* real size smaller than lua_Integer? */
    if (issigned)
    { /* needs sign extension? */
      lua_Unsigned mask = (lua_Unsigned)1 << (size * NB - 1);
      res = ((res ^ mask) - mask); /* do sign extension */
    }
  }
  else if (size > SZINT)
  { /* must check unread bytes */
    int mask = (!issigned || (lua_Integer)res >= 0) ? 0 : MC;
    for (i = limit; i < size; i++)
    {
      if ((unsigned char)str[islittle ? i : size - 1 - i] != mask)
        luaL_error(L, "%d-byte integer does not fit into Lua Integer", size);
    }
  }
  return (lua_Integer)res;
}

static int str_unpack(lua_State *L)
{
  Header h;
  const char *fmt = luaL_checkstring(L, 1);
  size_t ld;
  const char *data = luaL_checklstring(L, 2, &ld);
  size_t pos = (size_t)posrelat(luaL_optinteger(L, 3, 1), ld) - 1;
  int n = 0; /* number of results */
  luaL_argcheck(L, pos <= ld, 3, "initial position out of string");
  initheader(L, &h);
  while (*fmt != '\0')
  {
    int size, ntoalign;
    KOption opt = getdetails(&h, pos, &fmt, &size, &ntoalign);
    if ((size_t)ntoalign + size > ~pos || pos + ntoalign + size > ld)
      luaL_argerror(L, 2, "data string too short");
    pos += ntoalign; /* skip alignment */
    /* stack space for item + next position */
    luaL_checkstack(L, 2, "too many results");
    n++;
    switch (opt)
    {
    case Kint:
    case Kuint:
    {
      lua_Integer res = unpackint(L, data + pos, h.islittle, size,
                                  (opt == Kint));
      lua_pushinteger(L, res);
      break;
    }
    case Kfloat:
    {
      volatile Ftypes u;
      lua_Number num;
      copywithendian(u.buff, data + pos, size, h.islittle);
      if (size == sizeof(u.f))
        num = (lua_Number)u.f;
      else if (size == sizeof(u.d))
        num = (lua_Number)u.d;
      else
        num = u.n;
      lua_pushnumber(L, num);
      break;
    }
    case Kchar:
    {
      lua_pushlstring(L, data + pos, size);
      break;
    }
    case Kstring:
    {
      size_t len = (size_t)unpackint(L, data + pos, h.islittle, size, 0);
      luaL_argcheck(L, pos + len + size <= ld, 2, "data string too short");
      lua_pushlstring(L, data + pos + size, len);
      pos += len; /* skip string */
      break;
    }
    case Kzstr:
    {
      size_t len = (int)strlen(data + pos);
      lua_pushlstring(L, data + pos, len);
      pos += len + 1; /* skip string plus final '\0' */
      break;
    }
    case Kpaddalign:
    case Kpadding:
    case Knop:
      n--; /* undo increment */
      break;
    }
    pos += size;
  }
  lua_pushinteger(L, pos + 1); /* next position */
  return n + 1;
}

/* }====================================================== */

static const luaL_Reg strlib[] = {
    {"byte", str_byte},
    {"char", str_char},
    {"dump", str_dump},
    {"find", str_find},
    {"format", str_format},
    {"gmatch", gmatch},
    {"gsub", str_gsub},
    {"len", str_len},
    {"lower", str_lower},
    {"match", str_match},
    {"rep", str_rep},
    {"reverse", str_reverse},
    {"sub", str_sub},
    {"upper", str_upper},
    {"pack", str_pack},
    {"packsize", str_packsize},
    {"unpack", str_unpack},
    {NULL, NULL}};

static void createmetatable(lua_State *L)
{
  lua_createtable(L, 0, 1);       /* table to be metatable for strings */
  lua_pushliteral(L, "");         /* dummy string */
  lua_pushvalue(L, -2);           /* copy table */
  lua_setmetatable(L, -2);        /* set table as metatable for strings */
  lua_pop(L, 1);                  /* pop dummy string */
  lua_pushvalue(L, -2);           /* get string library */
  lua_setfield(L, -2, "__index"); /* metatable.__index = string */
  lua_pop(L, 1);                  /* pop metatable */
}

/*
** Open string library
*/
LUAMOD_API int luaopen_string(lua_State *L)
{
  luaL_newlib(L, strlib);
  createmetatable(L);
  return 1;
}
